/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.result.method.annotation;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.core.MethodParameter;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.MatrixVariable;
import org.springframework.web.bind.annotation.ValueConstants;
import org.springframework.web.reactive.HandlerMapping;
import org.springframework.web.server.ServerErrorException;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.ServerWebInputException;

/**
 * Resolves arguments annotated with {@link MatrixVariable @MatrixVariable}.
 *
 * <p>If the method parameter is of type {@link Map} it will by resolved by
 * {@link MatrixVariableMapMethodArgumentResolver} instead unless the annotation
 * specifies a name in which case it is considered to be a single attribute of
 * type map (vs multiple attributes collected in a map).
 *
 * @author Rossen Stoyanchev
 * @see MatrixVariableMapMethodArgumentResolver
 * @since 5.0.1
 */
public class MatrixVariableMethodArgumentResolver extends AbstractNamedValueSyncArgumentResolver {

    public MatrixVariableMethodArgumentResolver(
            @Nullable ConfigurableBeanFactory factory, ReactiveAdapterRegistry registry) {

        super(factory, registry);
    }


    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return checkAnnotatedParamNoReactiveWrapper(parameter, MatrixVariable.class,
                (ann, type) -> !Map.class.isAssignableFrom(type) || StringUtils.hasText(ann.name()));
    }


    @Override
    protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
        MatrixVariable ann = parameter.getParameterAnnotation(MatrixVariable.class);
        Assert.state(ann != null, "No MatrixVariable annotation");
        return new MatrixVariableNamedValueInfo(ann);
    }

    @Nullable
    @Override
    protected Object resolveNamedValue(String name, MethodParameter param, ServerWebExchange exchange) {
        Map<String, MultiValueMap<String, String>> pathParameters =
                exchange.getAttribute(HandlerMapping.MATRIX_VARIABLES_ATTRIBUTE);
        if (CollectionUtils.isEmpty(pathParameters)) {
            return null;
        }

        MatrixVariable ann = param.getParameterAnnotation(MatrixVariable.class);
        Assert.state(ann != null, "No MatrixVariable annotation");
        String pathVar = ann.pathVar();
        List<String> paramValues = null;

        if (!pathVar.equals(ValueConstants.DEFAULT_NONE)) {
            if (pathParameters.containsKey(pathVar)) {
                paramValues = pathParameters.get(pathVar).get(name);
            }
        }
        else {
            boolean found = false;
            paramValues = new ArrayList<>();
            for (MultiValueMap<String, String> params : pathParameters.values()) {
                if (params.containsKey(name)) {
                    if (found) {
                        String paramType = param.getNestedParameterType().getName();
                        throw new ServerErrorException(
                                "Found more than one match for URI path parameter '" + name +
                                        "' for parameter type [" + paramType + "]. Use 'pathVar' attribute to disambiguate.",
                                param, null);
                    }
                    paramValues.addAll(params.get(name));
                    found = true;
                }
            }
        }

        if (CollectionUtils.isEmpty(paramValues)) {
            return null;
        }
        else if (paramValues.size() == 1) {
            return paramValues.get(0);
        }
        else {
            return paramValues;
        }
    }

    @Override
    protected void handleMissingValue(String name, MethodParameter parameter) throws ServerWebInputException {
        String paramInfo = parameter.getNestedParameterType().getSimpleName();
        throw new ServerWebInputException("Missing matrix variable '" + name + "' " +
                "for method parameter of type " + paramInfo, parameter);
    }


    private static final class MatrixVariableNamedValueInfo extends NamedValueInfo {

        private MatrixVariableNamedValueInfo(MatrixVariable annotation) {
            super(annotation.name(), annotation.required(), annotation.defaultValue());
        }
    }

}
